1. Technical Field
The present invention relates generally to wrapping material onto a device. More particularly, the present invention relates to a method and apparatus for coiling a film of material onto a device such as a pin or spool, where the material is coiled without wrinkling or twisting, despite variations in the thickness of the film.
2. Description of Related Art
Where applicable, using a device such as a spool, reel, or pin, to collect, store, and dispense materials is convenient and common with such everyday end products as carpet, paper, aluminum foil, and garbage bags. In addition, it is common and convenient to use such devices to collect, store, and dispense materials for use in further manufacturing steps.
Depending on the type of material being processed and intended future use, different mechanisms may be employed to effectively use a spool to collect a material. Variables such as speed, tension, and the amount of material stored on a spool may need to be adjusted for different applications.
In the snack food industry, for example, films of packaging material are commonly coiled onto spools and later dispensed in further manufacturing steps. The process of winding such packaging material onto a spool, reel, or pin is best described by referring to FIGS. 1a and 1b. FIG. 1a shows a typical spiral winder of the prior art. FIG. 1b shows the same prior art spiral winder with a film of material 10 being supplied to the winder and collected onto a spool 20. For purposes of this application, a spool may be any kind of rotatable collecting device, such as a reel, pin, bobbin, or spool. Also shown in FIG. 1b are an upper guide 80 and lower guide 90 that provide tension and direction to the material 10 as it is gathered onto the spool 20. The upper guide 80 and lower guide 90 maximize the of material stored on any one spool 20, and ensure the material 10 is coiled tightly and evenly on the spool 20, so the coiled configuration itself is structurally secure and stable. In addition, the upper guide 80 and lower guide 90 ensure that the material 10 is coiled smoothly in order to avoid folds or wrinkles. The configuration in FIG. 1b is ideally employed where the material being coiled 10 is of uniform thickness.
Referring to FIG. 1c, in certain applications the material 10 being collected onto a spool 20 may vary in thickness across its width 170. An example of this known to Applicants is where the material 10 being collected on a spool 20 is a continuous sheet of material 10, having a zipper seal 30 attached along the length of the sheet 10, that will later be used to form re-closable pouches. In such instances, use of a spiral winder of the prior art, such as the one in FIG. 1e, leads to problems.
Referring again to FIG. 1c, consider the situation presented when processing material that will later be used to form re-closable pouches. The area of the re-closable seal 30 is visible along one edge of the sheet of material 10. The difference between the thickness of the sheet 10 in the area of the re-closable seal 30, and the thickness of the remainder of the sheet, may be significant when attempting to effectively coil the material 10 onto the spool 20.
One of the problems caused by coiling a material 10 onto a spool 20 using a spiral winder of the prior art, where there is some variation in thickness along the width of the material 170, is that less material may be stored on a single spool. Reducing the amount of material stored per spool in a high volume production environment greatly increases production costs.
Telescoping is another problem caused by such a variation in thickness along the width of a material collected on a spool. A film thickness variation causes one side of the to be coiled much thicker and tighter than the other. The differences in thickness and tautness result in the spool of material having an unstable character. Once coiling of a material onto a spool or pin is complete, it may be necessary to remove the coiled material from the spiral winder. Upon removal of the spool of material from the winder, the coiled material may telescope to the loose side of the coil such that the material is no longer contained in a coiled configuration at all, but takes on a conic or telescopic shape. Loss of the coiled configuration renders that configuration unrecoverable without tedious and time-consuming unraveling, causes the spool of material to be unsuitable for use in further processes, and often results in loss of product.
Referring again to FIG. 1c, one prior art proposed solution to this problem known to applicants calls for the spool 20, as it collects material, to move laterally, back and forth, along its axis of rotation 140. This motion resembles that of a fishing reel as the film of material 10 wraps onto the spool 20, while the spool 20 oscillates along its axis 140 to distribute the film. Although employment of this technique allows more material to be collected on each spool and prevents the coiled configuration from telescoping, other problems are presented. The back and forth lateral motion of the spool 20 along its axis 140, together with the inflexible restraint provided by the upper guide 80 and lower guide 90, causes the tension in the material 10 to vary along the material""s width 170 as it is wrapped. This variation in tension along the width of the material 170 as it is wrapped results in slack along one edge of the material and corresponding variations in tightness between layers of the coiled material on the oscillating spool. In any given region where such a variation in tightness between layers is present, the material in that region in a preceding layer on the spool may be loose enough that a following, tighter layer causes the material of the preceding layer to wrinkle in the region. Such wrinkling and folding may become permanent and large portions of material cosmetically unacceptable for ultimate sale. Wrinkling may also render materials unable to be used in further processes that require the materials to be smooth. In addition, wrinkling may ultimately cause failure in the structure of the material, resulting in cracks or holes in the material.
Consequently, what is needed is a spiral winder that is capable of processing material of uniform or varying thickness. Despite any thickness variations, the spiral winder must be capable of wrapping materials onto a spool without folds or wrinkles in order to avoid defects in further processes and end-user products. Additionally, as a spiral winder wraps a material onto a spool, the winder must maintain a uniform tension on the material and distribute the material evenly on the spool in order to maximize spool capacity and form a roll stable enough to be transported, stored, or used to dispense the material to product end-users or further processes.
The proposed invention comprises a spiral winder that winds materials onto a spool and compensates for thickness variations along the width of a film of material. The compensations are accomplished by horizontal oscillations of the spool and by employing a pivoting guide roller to maintain uniform tension on the material as it is coiled onto the spool.
By accounting for variations in film thickness, the present invention maximizes spool capacity, prevents folds and wrinkles that result in loss of product, and ensures the stability of the resulting roll of material necessary for further processing.